This invention relates to a nutrient supply system for hydroponic systems. In particular, this invention relates to a nutrient supply system that utilizes only an air pump to supply nutrient solution to a hydroponic system.
Hydroponics is the science of growing plants without soil. In recent years, hydroponics has become much more popular due to the limited space in most urban environments. Hydroponic systems offer an economical solution that will allow the utilization of unused space such as the rooftops of urban buildings, or other available space.
A hydroponic system typically has two main parts, a plant container, and a nutrient supply system to supply nutrients and water to the plant container. In the development of early hydroponic systems that would produce consistently, a number of problems arose. Early systems had problems in continuously supplying, and accurately metering, nutrient solution to the plant containers. It is important that the proper amount of nutrients, which are normally in a water base, are supplied to the plants. Also, a gentle, predictable flow of nutrients is desirable. Of course, if too little solution is supplied the plants will die.
Thus, it is important that a nutrient supply system for a hydroponic system be able to supply sufficient solution to feed the plants while at the same time accurately meter the amount of solution to ensure that too much solution is not supplied to the plants.
It is also important that all components of a hydroponic system be economical. Any practical hydroponic system must be inexpensive and reliable.
Most early nutrient supply systems utilized chemical feed pumps to supply the nutrient solution directly to plant containers. Chemical feed pumps are notoriously complicated and require that extreme measures to be taken to ensure that the pump motor is sealed from the nutrient solution. The nutrient solution is corrosive to the motor of the pump, and it is necessary that the pump chamber be completely sealed from the motor chamber. This results in a complex and costly pumping system. Also, these pumps often supply unnecessarily large amounts of fluid. For this reason, air pumps were utilized to supply air as a motive fluid to move the nutrient solution to the plant container.
In Soviet Pat. No. 238,945, a nutrient supply system is disclosed wherein the nutrient chamber is sealed off by a diaphragm and high-pressure air is sent to the top of the diaphragm, thus pushing it downwardly upon the nutrient solution. The downward force of the air pressure against the diaphragm caused the nutrient solution to be driven through a supply line to the plant containers of the hydroponic system. This type of supply system avoided the problems inherent in a system utilizing a chemical feed pump; however, problems still remained with this system. It is difficult to accurately meter the fluid with this type of supply system, since many variables are involved. The height of the nutrient container creates gravity force that could end up supplying some nutrient fluid to the plant containers. In addition, the relative strength of the diaphragm, the density of the nutrient solution and the exact pressure of the high-pressure air utilized to move the fluid must all be considered when attempting to accurately meter the nutrient solution. These variables could result in an unexpectedly large amount of nutrient solution being sent to the plant containers or, alternatively, an insufficient amount being sent to the plant containers.
A further problem with a system such as illustrated by Soviet Pat. No. 238,945 is that the chamber to which the high-pressure air is sent must be perfectly sealed in order to ensure that the desired pressure is maintained within the chamber.
Another supply system is shown in Soviet Pat. No. 1,099,876. This system is similar to that shown in the previous Soviet patent; however, it does not use a diaphragm to seal the nutrient chamber. High-pressure air is communicated directly to the top of the nutrient solution. This eliminates the problem of considering the diaphragm strength when determining the amount of pressurized air to be sent to the container to accurately meter the fluid. However, the other problems still remain. Namely, the elevation of the nutrients container, the exact pressure of the high-pressure air entering the system, and the densities of the nutrient solution are all factors which determine how much of the nutrient solution is being sent to the plant containers. Also, the high-pressure air chamber must still be sealed from leaking to the atmosphere in order to accurately meter the solution.
Another type of supply system is illustrated in the article "A Mechanism for the Automatic Irrigation of Sand Cultures." This article was published in the July 1, 1938 issue of Science at page 17. In this system, the top of a nutrient container has a stopper which has a fluid supply line, a fluid return line and an air pressure line extending through it. This type of supply system is similar to the previously-described Soviet Pat. No. 1,099,876. In addition to having the problems associated with the Soviet reference, this system utilizes an extremely complex control for regulating the flow of air to the system and is thus undesirable.
Soviet Pat. No. 386,607 shows an alternative type of nutrient supply system where a pressure air line is communicated to the bottom of a nutrient supply container to drive nutrient solution up a supply line. This type of system, known as a "bubble-up" pumping system is inherently difficult for accurate metering of fluid. In particular, the distance between the supply tube bottom and the container wall, the relative densities of the fluid and the air, and the exact amount of air being sent to the system would all be factors that would need to be considered in accurately metering the fluid. In addition, the Soviet reference does not show any means for returning the nutrient solution from the plant containers back to the nutrient container. If there is some means for returning the solution, the container cannot be completely sealed off as it is apparently illustrated as being. The return flow of fluid to the solution would increase the amount of air in the solution, thus lowering the efficiency of this type of pumping mechanism.
A nutrient supply system is illustrated in U.S. Pat. No. 4,302,906. In this patent, a system is disclosed in which air is communicated to the bottom of a tube to "bubble-up" the nutrient solution within the tube. A return line is also included to return fluid back to the system. This type of system has all the problems noted with Soviet Pat. No. 386,607.
Another type of pumping arrangement that has been utilized to move nutrient solution is a venturi or jet pump. This type of pump can be understood from U.S. Pat. No. 2,131,743. In this patent, high-pressure air is sent through a venturi nozzle and a line to a pump fluid is disposed downstream of this nozzle. The fluid is drawn up the line and entrained along with the high-velocity jet that is created by the nozzle. In this type of pump, the elevation of the fluids is not normally a concern, and it is not necessary that the entire chamber be air tight. For these reasons, this type of pump is useful for accurately metering an amount of fluid to be pumped. This patent, however, does not disclose the use of this type of pump in any type of nutrient supply system.
The use of a venturi or jet pump with a nutrient supply system for hydroponic systems is illustrated in an article entitled "Automatic Subirrigation Sand Culture Technique for Comparative Studies in Plant Nutrition." This article was published in Laboratory Practices, Vol. 23, No. 1, January 1974 at pp. 20-1. In this system, a nutrient supply container has a single line leading to a plant container. A jet of high-pressure air is communicated to the line at a point between the nutrient container and the plant container. This jet of fluid accurately meters nutrient solution from the nutrient solution container to the plant container. However, this single line is utilized as both a supply and a return line. In addition, since the high-pressure air line is communicated to the supply line outside the container, a relatively complex system results. It is to be understood that these lines are rather delicate, and it is undesirable to have them positioned outside of the container since they can be easily jostled and disconnected. In addition, having the air supply line entering a flexible tube is undesirable since the relative position of the air line within the flexible tube can easily change. It is important that the air line be accurately positioned with respect to the fluid supply tube to ensure proper metering of the fluid.
It is also undesirable to return the nutrient solution through the same line that is supplying the solution. Since the above system utilizes only one line the pump will frequently end up supplying only returning solution. This returning solution normally has a lower nutrient concentration than the solution in the nutrient solution container.
Another problem with utilizing a venturi or jet pump for supplying nutrient solutions is that the narrow fluid supply line can easily become encrusted wi(h the nutrient solution.
It is therefore an object of the present invention to disclose a relatively simple nutrient supply system for use with hydroponic systems.
It is further an object of the present invention to disclose a nutrient supply system that will accurately meter the nutrient solution to the plant containers.
It is further an object of the present invention to disclose such a nutrient supply system that will be relatively sturdy and not easily jostled so as to interfere with the accurate metering of the nutrient solution.
Moreover, it is an object of the present invention to create a system that is relatively inexpensive and requires little attention to ensure proper functioning.